This invention relates to the recovery of active tannin from schoene sludge in a beer production plant whereby the tannin can be reused in making beer.
In order to be commercially acceptable, a beer must possess certain properties; for example, it must be sparkling clear. An additional property which is most significant to beer connoisseurs is referred to as chill stability. This relates to the property noted above as "sparkling clear". As the name "chill haze" implies, a haze usually forms in beer when it is chilled. As the temperature of the beer is returned to room temperature, the haze usually disappears, only to reappear upon subsequent rechilling.
Several methods are used in the brewing industry for chillproofing of beer, the method of choice depending on the process economics and on the flavor characteristics desired in the end product.
One of the methods widely used in the trade for chillproofing of beer is based on the precipitation and removal of proteinaceous constituents from beer using a solution of tannic acid derived from plants. Other methods of precipitation include bentonite and silica gel addition.
This invention relates to the chillproofing process using tannic acid. One of the ways tannic acid (tannin) is added to the beer from a lager tank as it enters a schoene or chillproofing tank. In the schoene tank, the tannin reacts with proteins to form what is called a "schoene sludge" which precipitates out. The clear beer is decanted off and undergoes further clarification. The sludge is the material which is the subject of this invention.
"Tannin" is a generic term for substances able to form complexes with proteins and protein-like substances. Most tannins are some type of polyphenol, but not all polyphenols are tannins. Presently, commercial tannins are purchased from manufacturers and are used in the beer chillproofing process. These commercial tannins are of the hydrolyzable gallotannin type and are homologous mixtures of many gallotannins. Most of the gallotannins presently used in chillproofing are composed of two compounds, glucose and gallic acid.
Many different arrangements and ratios of gallic acid:glucose are present in gallotannins. The different ratios produce different molecular sizes and different arrangements produce isomers which are compounds of the same empirical formula but different structural arrangement.
Commercial tannins presently are made from gallnuts and sumac leaves. The tannins are extracted from natural sources with methyl isobutyl ketone and water or acetone and water, purified and spray dried.
When the tannin is added to the beer in the schoene process, it bonds to some of the proteins, peptides and carbohydrates in the beer to form what is called "schoene sludge". Yeast is also co-precipitated. The bonding is strong and is believed to be of three types: hydrogen bonding between phenolic and protein ketoimide groups; hydrophobic interactions between the aromatic ring structures and the hydrophobic regions of proteins; and ionic bonding between the phenolate anion and the cationic site of the protein molecule.
Traditionally the sludge is discarded. However, present day environmental regulations make this costly. Also, the tannin is expensive and it would be advantageous to reuse it. Furthermore, the residue from the sludge separation is more acceptable as animal feed if the tannins are removed as animals cannot digest tannin material properly.
Accordingly it is a principal object of this invention to provide a process for recovering chillproofing active tannin from schoene sludge produced in a beer making process. It is important that the tannin retain its chillproofing properties as it is possible to recover tannin which is not active. Inactive material has no value in chillproofing of beer.
These and other objects and advantages will become apparent hereinafter.